The role of surface tension on the growth of bubbles by rectified diffusion.

Rectified diffusion has wide and important applications in sonochemistry, ultrasonic cleaning and medical ultrasound. Recent experimental results have demonstrated that the addition of surfactant substantially enhances bubble growth rate. As a hypothesis, this was widely attributed to the acoustic microstreaming and mass transfer resistance caused by surfactants. In this research, the effects of the surfactant of sodium dodecyl sulphate on the rectification have been simulated by considering only the variation of the surface tension coefficient due to the surfactant. The computations are carried out using a newly developed tractable model based on the multi-scale method and the method of matched asymptotic expansions, which allows the prediction of bubble growth taking place over millions of oscillation cycles. The rate of bubble growth observed in the experiments is accurately predicted by our computations, for a range for bulk surfactant SDS concentrations less than or equal to 2.4 mM. Contrary to the widely held hypothesis in the published literature, this has demonstrated that the dominant physical mechanisms remain the shell and area effects in this range of bulk surfactant concentrations. The further enhancement of bubble growth rate provided by either acoustic microstreaming or the resistance to mass transfer is only evident at higher bulk surfactant concentrations. Therefore, the role of surface tension in rectified diffusion for aqueous surfactant solutions is more significant than previously understood. The new results also show that the bubble growth rate is sensitive to small changes in the bubble radius which may account for its unpredictability in applications of sonochemistry.

Numerical investigation of cavitation generated by an ultrasonic dental scaler tip vibrating in a compressible liquid.

Bacterial biofilm accumulation around dental implants is a significant problem leading to peri-implant diseases and implant failure. Cavitation occurring in the cooling water around ultrasonic scaler tips can be used as a novel solution to remove debris without any surface damage. However, current clinically available instruments provide insufficient cavitation around the activated tip surface. To solve this problem a critical understanding of the vibro-acoustic behaviour of the scaler tip and the associated cavitation dynamics is necessary. In this research, we carried out a numerical study for an ultrasound dental scaler with a curved shape tip vibrating in water, using ABAQUS based on the finite element method. We simulated the three-dimensional, nonlinear and transient interaction between the vibration and deformation of the scaler tip, the water flow around the scaler and the cavitation formation and dynamics. The numerical model was well validated with the experiments and there was excellent agreement for displacement at the free end of the scaler. A systematic parametric study has been carried out for the cavitation volume around the scaler tip in terms of the frequency, amplitude and power of the tip vibration. The numerical results indicate that the amount of cavitation around the scaler tip increases with the frequency and amplitude of the vibration. However, if the frequency is far from the natural frequency, the cavitation volume around the free end decreases due to reduced free end vibration amplitude.

Impact of operative time on early joint infection and deep vein thrombosis in primary total hip arthroplasty.

PURPOSE: Infections and deep vein thrombosis (DVT) after total hip arthroplasty (THA) are challenging problems for both the patient and surgeon. Previous studies have identified numerous risk factors for infections and DVT after THA but have often been limited by sample size. We aimed to evaluate the effect of operative time on early postoperative infection as well as DVT rates following THA. We hypothesized that an increase in operative time would result in increased odds of acquiring an infection as well as a DVT. METHODS: We conducted a retrospective analysis of prospectively collected data using the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database from 2006 to 2015 for all patients undergoing primary THA. Associations between operative time and infection or DVT were evaluated with multivariable logistic regressions controlling for demographics and several known risks factors for infection. Three different types of infections were evaluated: (1) superficial surgical site infection (SSI), an infection involving the skin or subcutaneous tissue, (2) deep SSI, an infection involving the muscle or fascial layers beneath the subcutaneous tissue, and (3) organ/space infection, an infection involving any part of the anatomy manipulated during surgery other than the incisional components. RESULTS: In total, 103,044 patients who underwent THA were included in our study. Our results suggested a significant association between superficial SSIs and operative time. Specifically, the adjusted odds of suffering a superficial SSI increased by 6% (CI=1.04-1.08, p<0.0001) for every 10-minute increase of operative time. When using dichotomized operative time (<90minutes or >90minutes), the adjusted odds of suffering a superficial SSI was 56% higher for patients with prolonged operative time (CI=1.05-2.32, p=0.0277). The adjusted odds of suffering a deep SSI increased by 7% for every 10-minute increase in operative time (CI=1.01-1.14, p=0.0335). No significant associations were detected between organ/space infection, wound dehiscence, or DVT and operative time either as continuous or as dichotomized. CONCLUSION: Prolonged operative times (>90min) are associated with increased rates of superficial SSIs, but not deep SSIs, organ/space infections, wound dehiscence, or DVT. LEVEL OF EVIDENCE: III.

International field trials of pyrethroid-treated wood exposed to Coptotermes acinaciformis in Australia and Coptotermes formosanus (Isoptera: Rhinotermitidae) in China and the United States.

Coptotermes Wasmann is one of the most important genera of wood-destroying insect pests, both in its native and introduced countries. Pyrethroids are among the most widely used insecticides in wood preservation around the world. Consequently, they have often been evaluated against different species of Coptotermes. However, because various test methods have been used between countries, comparing results is problematic. These field trials, using a single aboveground method of exposure, assessed a range of retentions of two pyrethroids (bifenthrin and permethrin) in Pinus radiata D. Don sapwood against two species of Coptotermes in three countries to provide directly comparable results. Coptotermes acinaciformis (Froggatt) in Australia consumed the most nontreated wood, followed by Coptotermes formosanus Shiraki in China, then C. formosanus in the United States, although these data were not significantly different. Both termite species demonstrated a dose-response to wood treated with the two pyrethroids; less wood was consumed as retention increased. Overall, C. acinaciformis consumed relatively little of the treated wood. In comparison, C. formosanus consumed 20-90% of the wood treated at the lowest retentions of the pyrethroids evaluated. Results indicated that C. acinaciformis was more sensitive to pyrethroid toxicity/repellency compared with C. formosanus. Factors that may have influenced the results are discussed. However, using a single aboveground method of exposure across three countries, that suited both species of Coptotermes, made it possible to determine unambiguously the actual differences between the species in their tolerances to the two pyrethroid insecticides.

Central bone grafting for nonunion of fractures of the tibia: a retrospective series.

Nonunion of the tibia associated with bone loss, previous infection, obliteration of the intramedullary canal or located in the distal metaphysis poses a challenge to the surgeon and significant morbidity to patients. We retrospectively reviewed the records of 24 patients who were treated by central bone grafting and compared them to those of 20 who were treated with a traditional posterolateral graft. Central bone grafting entails a lateral approach, anterior to the fibula and interosseous membrane which is used to create a central space filled with cancellous iliac crest autograft. Upon consolidation, a tibiofibular synostosis is formed that is strong enough for weight-bearing. This procedure has advantages over other methods of treatment for selected nonunions. Of the 24 patients with central bone grafting, 23 went on to radiographic and clinical union without further intervention. All healed within a mean of 20 weeks (10 to 48). No further bone grafts were required, and few complications were encountered. These results were comparable to those of the 20 patients who underwent posterolateral bone grafting who united at a mean of 31.3 weeks (16 to 60) but one of whom required below-knee amputation for intractable sepsis. Central bone grafting is a safe and effective treatment for difficult nonunions of the tibia.

New height, weight and head circumference charts for British children with Williams syndrome.

AIM: To produce a growth reference for British children with Williams syndrome. METHODS: The children and adults recruited into the study were all affiliated to the Williams Syndrome Foundation, a parent support group founded in 1979. They have all been shown to have a deletion of chromosome 7q11.23. One growth nurse (WRS) prospectively measured the weight, height and head circumference of individuals from 19 regions in Great Britain including Scotland, England and Wales. 169 children and adults were measured on up to four occasions between 2001 and 2004 (275 measurements). In addition, retrospective data were obtained from the hospital notes of 67 of these individuals (586 measurements). Centile curves were constructed using Cole's LMS method. RESULTS: The centile charts differ from charts previously derived in the USA and Germany and provide more appropriate standards for the British population. CONCLUSIONS: We propose that these charts be adopted for routine clinical practice as abnormalities in growth are an important feature of this syndrome.

Intramedullary nailing in open tibia fractures: a comparison of two techniques.

We analyzed 51 patients with open tibial fractures treated with intramedullary nailing. In 29 patients the nailing was performed without reaming and in 22 after the "reamed-to-fit" technique. There was no statistically significant difference in the rate of union. The nonreamed group required a greater number of secondary procedures to achieve union and had a higher but not statistically significant incidence of infection. Analysis of the operative and anesthesia cost associated with the additional procedures revealed that on average, patients receiving nonreamed nailing incurred a cost of $4,900 more per fracture than patients of the reamed-to-fit technique. The healing rates of open tibia fractures using either minimally reamed or nonreamed techniques of intramedullary nailing are comparable. No increase in the rate of infection with the reamed-to-fit technique was found. A significant increase in the number of secondary procedures required to achieve union was found with the nonreamed nailing technique.

Post-traumatic stress disorder among patients with chronic pain and chronic fatigue.

BACKGROUND: Fibromyalgia (FM), a chronic pain condition of unknown aetiology often develops following a traumatic event. FM has been associated with post-traumatic stress disorder (PTSD) and major depression disorder (MDD). METHOD: Patients seen in a referral clinic (N=571) were evaluated for FM and chronic fatigue syndrome (CFS) criteria. Patients completed questionnaires, and underwent a physical examination and a structured psychiatric evaluation. Critical components of the diagnostic criteria of FM (tender points and diffuse pain) and CFS (persistent debilitating fatigue and four of eight associated symptoms) were examined for their relationship with PTSD. RESULTS: The prevalence of lifetime PTSD was 20% and lifetime MDD was 42%. Patients who had both tender points and diffuse pain had a higher prevalence of PTSD (OR=3.4, 95% CI 2.0-5.8) compared with those who had neither of these FM criteria. Stratification by MDD and adjustment for sociodemographic factors and chronic fatigue revealed that the association of PTSD with FM criteria was confined to those with MDD. Patients with MDD who met both components of the FM criteria had a three-fold increase in the prevalence of PTSD (95% CI 1.5-7.1); conversely, FM patients without MDD showed no increase in PTSD (OR=1.3, 95% CI 0.5-3.2). The components of the CFS criteria were not significantly associated with PTSD. CONCLUSION: Optimal clinical care for patients with FM should include an assessment of trauma in general, and PTSD in particular. This study highlights the importance of considering co-morbid MDD as an effect modifier in analyses that explore PTSD in patients with FM.

Iliosacral screw fixation of the posterior pelvic ring using local anaesthesia and computerised tomography.

Various techniques have been used for the fixation of the posterior pelvis, each with disadvantages specific to the technique. In this study, a new protocol involving the placement of posterior pelvic screws in the CT suite is described and evaluated. A total of 66 patients with unstable pelvic ring injuries was stabilised under local anaesthesia with sedation. The mean length of time for the procedure was 26 minutes per screw. There were no technical difficulties or misplaced screws and no cases of infection or nonunion. All patients stated that they would choose to have the CT scan procedure again rather than a procedure requiring general anaesthesia. The charges for the procedure were approximately 1840 pounds sterling (2800 dollars) per operation. CT-guided placement of iliosacral screws is a safe, feasible, and cost-effective alternative to radiologically-guided placement in the operating theatre in selected patients.

Survival analysis of posterior restorations using an insurance claims database.

This study indicates that composite restorations do not last as long as amalgam restorations in posterior teeth. Dentists can use this information to better inform their patients when choosing restorative materials.

Evolution of a multidisciplinary clinical pathway for the management of unstable patients with pelvic fractures.

OBJECTIVE: To determine whether the evolution of the authors' clinical pathway for the treatment of hemodynamically compromised patients with pelvic fractures was associated with improved patient outcome. SUMMARY BACKGROUND DATA: Hemodynamically compromised patients with pelvic fractures present a complex challenge. The multidisciplinary trauma team must control hemorrhage, restore hemodynamics, and rapidly identify and treat associated life-threatening injuries. The authors developed a clinical pathway consisting of five primary elements: immediate trauma attending surgeon's presence in the emergency department, early simultaneous transfusion of blood and coagulation factors, prompt diagnosis and management of associated life-threatening injuries, stabilization of the pelvic girdle, and timely insinuation of pelvic angiography and embolization. The addition of two orthopedic pelvic fracture specialists led to a revision of the pathway, emphasizing immediate emergency department presence of the orthopedic trauma attending to provide joint decision making with the trauma surgeon, closing the pelvic volume in the emergency department, and using alternatives to traditional external fixation devices. METHODS: Using trauma registry and blood bank records, the authors identified pelvic fracture patients receiving blood transfusions in the emergency department. They analyzed patients treated before versus after the May 1998 revision of the clinical pathway. RESULTS: A higher proportion of patients in the late period had blood pressure less than 90 mmHg (52% vs. 35%). In the late period, diagnostic peritoneal lavage was phased out in favor of torso ultrasound as a primary triage tool, and pelvic binding and C-clamp application largely replaced traditional external fixation devices. The overall death rate decreased from 31% in the early period to 15% in the later period, as did the rate of deaths from exsanguination (9% to 1%), multiple organ failure (12% to 1%), and death within 24 hours (16% to 5%). CONCLUSIONS: The evolution of a multidisciplinary clinical pathway, coordinating the resources of a level 1 trauma center and directed by joint decision making between trauma surgeons and orthopedic traumatologists, has resulted in improved patient survival. The primary benefits appear to be in reducing early deaths from exsanguination and late deaths from multiple organ failure.

Emergency medical services telephone referral program: an alternative approach to nonurgent 911 calls.

OBJECTIVE: To examine the effects of transferring nonurgent 911 calls to a telephone consulting nurse. It was hypothesized that the telephone referral program would result in fewer basic life support (BLS) responses with no adverse patient outcome or decrease in patient satisfaction. METHODS: A two-phased prospective study was conducted in an urban and rural setting with a population of 650,000. During phase I, a BLS unit was dispatched on all calls and a nurse intervention was simulated. During phase II, no BLS unit was dispatched for calls meeting study criteria. Callers were transferred to the nurse, and consulting nurse protocols were used to direct care. Data were collected from dispatch, BLS, nurse, and hospital records and patient self-assessment. RESULTS: During phase I, 38 callers were transferred to the consulting nurse with no nurse intervention. During phase II, 133 cases were transferred to the nurse line. There were no adverse outcomes detected. The nurse recommended home care for 31%, physician referral for 24%, referral back to 911 for 17%, community resource for 11%, and other referral for 17%. Nurses contacted 85 patients for telephone follow-up. Ninety-four percent of the patients reported feeling better, 6% felt the same, and none felt worse. Patients were satisfied with the outcome in 96% of the cases. CONCLUSION: Transferring 911 calls to a nurse line resulted in fewer BLS responses and no adverse patient outcomes, while maintaining high patient satisfaction. Dispatch criteria correctly identified cases with minimal medical needs. A high percentage of the patients reported feeling better after the intervention. This study has major implications for communities interested in efficient use of emergency medical services resources.

Removal of an intrathoracic migrated fixation pin by thoracoscopy.

Migration of orthopedic fixation pins into the thoracic cavity can result in perforation of pulmonary vasculature, aorta, bronchus, atrium, or ventricle. Prompt diagnosis and treatment is tantamount in preventing devastating consequences. A patient who had fixation of a right humeral fracture weeks later had intrathoracic migration of a fixation pin, found by routine postoperative radiographic examination. Because the patient was asymptomatic, we removed the pin with a thoracoscopic operation. The foreign body was retrieved successfully without intraoperative or postoperative complication.

Evidence for the effectiveness of techniques To change physician behavior.

STUDY OBJECTIVES: To understand the theory and results of how to improve physician performance, as part of overall health-care quality improvement. In particular, to study whether and how guideline production and dissemination affects physician performance. DESIGN: Review of meta-analyses and structured reviews; review of behavior change theories implicit in interventions to change physician performance. SETTING: Primarily the United States. PATIENTS OR PARTICIPANTS: Various patients and physicians, determined by reviews. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: There is no unifying theory of physician behavior change tested among physicians in practice. Attempts to affect individual physicians' performance have often met with failure. Mixed results are found for almost all interventions reviewed. Multiple interventions yield better results. CONCLUSIONS: The answer to the question of what works to improve an individual physician's clinical performance is not simple. Emerging theory and evidence suggests that applications of behavior-change methods should not be focused on which tools (don't) always work. Instead, guideline development and implementation methods should be theory driven and evidence based (supported by evidence that proves the theory correct). In particular, the framework of evidence-based quality assessment offers some insight into past failures and offers hope for organizing attempts at guideline implementation.

Results of report cards for patients with congestive heart failure depend on the method used to adjust for severity.

BACKGROUND: The validity of outcome report cards may depend on the ways in which they are adjusted for risk. OBJECTIVES: To compare the predictive ability of generic and disease-specific survival prediction models appropriate for use in patients with heart failure, to simulate outcome report cards by comparing survival across hospitals and adjusting for severity of illness using these models, and to assess the ways in which the results of these comparisons depend on the adjustment method. DESIGN: Analysis of data from a prospective cohort study. SETTING: A university hospital, a Veterans Affairs (VA) medical center, and a community hospital. PATIENTS: Sequential patients presenting in the emergency department with acute congestive heart failure. MEASUREMENTS: Unadjusted 30-day and 1-year mortality across hospitals and 30-day and 1-year mortality adjusted by using disease-specific survival prediction models (two sickness-at-admission models, the Cleveland Health Quality Choice model, the Congestive Heart Failure Mortality Time-Independent Predictive Instrument) and generic models (Acute Physiology and Chronic Health Evaluation [APACHE] II, APACHE III, the mortality prediction model, and the Chadson comorbidity index). RESULTS: The community hospital's unadjusted 30-day survival rate (85.0%) and the VA medical center's unadjusted 1-year survival rate (60.9%) were significantly lower than corresponding rates at the university hospital (92.7% and 67.5%, respectively). No severity model had excellent ability to discriminate patients by survival rates (all areas under the receiver-operating characteristic curve < 0.73). Whether the VA medical center, the community hospital, both, or neither had worse survival rates on simulated report cards than the university hospital depended on the prediction model used for adjustment. CONCLUSIONS: Results of simulated outcome report cards for survival in patients with congestive heart failure depend on the method used to adjust for severity.

Significant other responses are associated with fatigue and functional status among patients with chronic fatigue syndrome.

OBJECTIVE: The predictive power of partners' responses to illness behavior for illness outcomes was investigated among couples in which one person had chronic fatigue syndrome (CFS). METHODS: One hundred nineteen participants who met case-definition criteria for CFS and were living with a significant other (SO) completed self-report measures of relationship satisfaction, responses of their SO to fatigue symptoms, and outcome measures of fatigue and functional status. RESULTS: The results indicated that more frequent solicitous SO responses to illness behavior were predictive of greater fatigue-related severity and bodily pain. Solicitous SO responses to fatigue behavior were particularly influential in the context of a satisfactory relationship. In highly satisfactory relationships, solicitous SO responses were associated with significantly greater fatigue severity and fatigue-related disability than in relationships characterized by low or average satisfaction. CONCLUSIONS: Solicitous SO responses to CFS-related symptoms are associated with poorer patient outcomes, especially in the context of a satisfactory intimate relationship. Because of the cross-sectional nature of the study, the direction of effects cannot be interpreted unambiguously. SOs may be inadvertently positively reinforcing illness-related behavior: Solicitous partners may help the patient more with tasks of daily living, thereby decreasing the patient's activity level, which may lead to deconditioning and disability. Alternatively, patients with more severe symptoms and disability may present more opportunities for concerned SO responses, which again may be heightened in the context of a caring, satisfactory relationship. In either case, the results suggest that additional research on the role of solicitous SO responses is warranted.

Effect of different types of Medicaid managed care on childhood immunization rates.

Medicaid managed care can improve access to prevention services, such as immunization, for low-income children. The authors studied immunization rates for 7,356 children on Medicaid in three managed care programs: primary care case management (PCCM; n = 4,605), a voluntary HMO program (n = 851), and a mandatory HMO program (n = 1,900). Immunization rates (3:3:1 series) in PCCM (78%) exceeded rates in the voluntary HMO program (71%), which in turn exceeded those in the mandatory HMO program (67%). Adjusting for race, urban residence, and gender, compared to children in PCCM, children in the voluntary HMO program were less likely to complete the 3:3:1 series (OR = 0.75, CI = 0.63, 0.90), and children in the mandatory HMO program were even less likely to complete the series (OR = 0.59, CI = 0.51, 0.68). Results differed by individual HMOs. Monitoring of outcomes for all types of managed care by Medicaid agencies is imperative to assure better disease prevention for low-income children.

Assessing Medicaid recipient access and satisfaction. Fee-for-service, case management, and capitation.

Medicaid increasingly requires enrollment in managed care programs. This study assessed access to care, satisfaction with care, and appointment wait times during the transition from fee for service to managed care using three annual Medicaid recipient surveys. There was little evidence of dissatisfaction or poorer access among managed care recipients. Fee-for-service recipients, compared to primary care case management, reported greater general (91 vs. 78%, p < .01) and specialty care access (92 vs. 80%, p < .01). When appointments were required, adult HMO enrollees, compared to case management, had longer waits for routine care in the second (5.8 +/- 8.2 days vs. 4.0 +/- 6.6) and third surveys (5.5 +/- 6.9 days vs. 3.8 +/- 7.3); waits for other appointments did not consistently differ by program. There were no significant program differences in overall satisfaction. Findings are tempered by the potential for response bias and geographic confounding. Continued monitoring is crucial to assure that access and satisfaction remain high in Medicaid managed care.